3,4 - dimethyl - 5 - fthylphenyl methyl carbamate

ABSTRACT

DISCLOSED IS 3,4-DIMETHYL-5-ETHYLPHENYL METHYL CARBAMATE, USEFUL AS AN INSECTICIDE.

United States Patent 3,564,600 3,4 DIMETHYL 5 ETHYLPHENYL METHYL CARBAMATE Jerome G. Kuderna, Jr., Modesto, Calif., and Donald D.

Phillips, Metuchen, N.J., assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 200,643, June 7, 1962. This application Feb. 24, 1964, Ser. No. 346,997

Int. Cl. C07c 101/12 US. Cl. 260479 1 Claim ABSTRACT OF THE DISCLOSURE Disclosed is 3,4-dimethyl-S-ethylphenyl methyl carbamate, useful as an insecticide.

This application is a continuation-in-part of our application Ser. No. 200,643, filed June 7, 1962 which issued Apr. 21, 1964 as US. Patent 3,130,122.

This invention relates to a novel aryl ester of methylcarbamic acid, and to its use as an insecticide, particularly for control of soil-dwelling insect life. As used herein, the terms, soil-dwelling insect life, and soil-dwelling insects, refer to insects which spend part or all of their life history in soil and/or on the surface of soil. Accordingly, the term, soil insecticide, as used herein refers to an insecticide which is applied on soil and/ or into soil for control of the soil-dwelling insects.

An important aspect of plant husbandry is the protection of the root systems of plants from attack by soildwelling insect life. Some of the important noxious soildwelling insects include: the seedcorn maggot, the onion maggot, the cabbage maggot, the turnip maggot, the carrot rust fly, the southern corn rootworm, the northern corn rootworm, the western spotted cucumber beetle, false wireworms and wireworms.

To be a successful soil insecticide a compound must possess many properties; relatively few classes of compounds have been found to possess a sufficient number of these properties to sufficient degree. Firstly, it must of course be an effective insecticide against the insect life found in the soil; it must kill by contact, since few if any insects ingest sufficient soil to be subjected to a lethal dosage of the insecticide, and some insects, such as the wireworm, do not consume the husk or hull or seed, where the insecticide would be concentrated if it were used in a seed treatment. Second, the successful insecticide must be one which is readily disseminated in the soil, being present in the soil in a form and location readily accessible to the insect life (it must not be strongly adsorbed by the soil), yet it must have physical properties such that it is not readily lost from the soilas by volatilization into the air, or by leaching from the soil when it is wetted by rain or during irrigation. Thirdly, the insecticide must not be toxic to seeds and plants in the soil at the insecticidally effective dosage, and must not damage seeds or roots in the soil in which it is disseminated. Fourthly, it must be persistent, to provide long-term protection of the plant. This requires that the insecticide be stable in the soil environment. Few effective insecticides are sufficiently stable under such conditions, for the soil environment imposes severe tests on the stability of compounds disseminated therein; water and oxygen are both present in the soil, subjecting the compound to hydrolytic and oxidative deterioration; chemicals in the soilin fact, the particles of clay and other minerals which go to make up the soiltend to degrade compounds introduced into the soil; microorganisms present in the soil tend to break down compounds present in the soil.

For about the past decade, only the halogenated hydrocarbons have been found to have the requisite combination of physical and chemical properties, together with the requisite toxicity to insects, required for a successful soil insecticide. Compounds such as DDT, aldrin, endrin, isodrin, dieldrin, lindane, heptachlor, chlordane, toxaphene and TDE have dominated the soil insecticide field. Such compounds have been very effective. However, unfortunately, soil-dwelling insects have developed resistance to such halogenated insecticides, so that in many cases the halogenated insecticides are no longer sufficiently effective. Other compounds, such as organophosphorus compounds, have been developed as soil insecticides, but few have proven entirely satisfactory. There is currently, therefore, a substantial need for effective soil insecticides which will replace, or at least supplement, the halogenated hydrocarbon insecticides.

There now has been found a nitrogen-containing compoundcontaining no halogenthat appears to possess to the necessary degree the necessary spectrum of properties required of a successful soil insecticide. This compound is the 3,4-dimethyl-S-ethyl-phenyl ester of methylcarbamic acid. This compound has been found to effectively control soil-dwelling insects for extended periods of time, including insects which are resistant to chlorinated insecticides. This new carbamate has been found to be a highly active insecticide, with great stability and long life in soil. Further, it has been found to be readily available in the soil, apparently not being adsorbed by the soil to any significant extent, yet are not readily lost from the soil. Such properties are demonstrated by the fact-as will be established by experimental evidence hereinafterthat not only is this new carbamate effective for a long period of time in soil against soil-dwelling insects, but for extended periods of time readily kills insects which contact the surface of mud and other forms of soil which has been sprayed or otherwise impregnated with the new carbamate.

This latter propertythe effectiveness against insects contacting soil which has been impregnated with the carbamateis of great importance when considered with reference to the campaign to eliminate malaria-carrying mosquitoes in tropical areas. This campaign aims at breaking the chain of malaria transmission by spraying dwellings and other buildings in malarial zones with an insecticide to kill mosquitoes which invade those buildings. To be effective for such a purpose, an insecticide must have long life. Further, because many buildings in malarial zonesparticularly in primitive areasare constructed of, and/ or are finished with absorptive materials, the insecticide must be one whose effectiveness is not lost or destroyed when it is impregnated upon such absorptive materials. Thus, in tropical malarial areas, buildings often are built of absorptive plant materials; further, in these and other malarial areas, buildings often are plastered with mud or a cementitious plaster materialtypes of materials which are highly absorptive. The discovery that the novel carbamate of this invention maintains its insecticidal effectiveness for extended periods of time on mud and like absorptive materials therefor fills an urgent need.

The carbamate of this invention can be characterized, by the formula:

This ester of methylcarbamic acid is readily prepared by reacting 3,4-dimethyl-5-ethyl-phenol with methyl iso- 3 cyanate in the presence of a catalytic amount of a catalyst such as a tertiary aliphatic amine.

The manner in which the ester is prepared is illustrated by the following example, which shows its preparation. In this example, parts means parts by weight unless otherwise indicated, with parts by weight bearing the same relation to parts by volume as does the kilogram to the liter.

EXAMPLE I Preparation of 3,4-dimethyl-5-ethylphenyl methyl carbamate Five parts of 3,4-dimethyl-S-ethylphenol was dissolved in a mixture of 35 parts by volume of anhydrous ether and 5 parts by volume of methyl isocyanate containing 0.1 part by volume of triethylamine. The mixture was held at room temperature for 3 days. The solvent was expelled over a steam bath; the residual oil solidified upon cooling. Recrystallization from ether gave 6.5 parts (95% yield) of 3,4-dimethyl-S-ethylphenyl methylcarbamate, melting point 92 C. The identity of the product was confirmed by elemental analysis.

Analysis (percent by weight).Calculated for C, 69.5; H, 8.2; N, 6.7. Found: C, 69.2; H, 8.3; N, 6.7.

As will be evident from the foregoing example, the reaction of the phenol and methyl isocyanate is most conveniently carried out in a suitable solvent, diethyl ether being quite suitable for this purpose. Further, the reaction is conveniently conducted at about room temperature. Moderately elevated temperatures-say, up to about 60 Cr-can in some cases be used to reduce the requisite reaction time. The carbamate product is ordinarily best recovered and purified by recrystallization techniques.

The carbamate of this invention possesses insecticidal activity and is an effective soil insecticide of extended life in soil, as is evidenced by the results of experiments set out in Example IV, following. It is to be understood that while the carbamate of this invention is primarily of interest as a soil insecticide-because it is effective in soil, and so few insecticides are-it also is useful as a general purpose insecticide, inasmuch as it is toxic to a variety of insect species.

By the term insects is meant not only the members of the class Insecta, but also related or similar invertebrate animal organisms belonging to the allied classes of arthropods and including ticks, mites, spiders, wood lice and the like.

The effectiveness of the compound of this invention as an insecticide is demonstrated by the following experiments and the results thereof.

EXAMPLE II Solutions of the novel compound of the invention were made up employing either a neutral petroleum distillate boiling within the kerosene range or acetone as the solvent. Tests were carried out using the common house fly, Musca domestica, as the test insect, the method used being that described by Y. P. Sun, Journal of Economic Entomology, vol. 43, pp. 45 et seq. (1950). Table I shows the concentration of toxic agent in the sprayed solution required to cause 50 percent mortality of the test insecti.e., the LC concentration. The activity of the compound of the invention with respect to the corn earworm, Heliothis zea, was determined by caging corn earworm larvae on cut broad bean plants inserted in water after formulations of the test compound, prepared by dissolving an acetone solution of the compound in water, had been sprayed thereon. Two replicates were used with each test, various tests being directed to different concentrations of the test compounds in the liquid formulations. The LC values are set out on Table I. The activity of the compound of the invention with respect to the rice weevil, Sitoplzilus oryzae, was determined by pouring a measured amount of a solution of the test compound over adult rice weevils in a container having a perforated bottom, excess solution immediately draining away. Ten seconds after the solution had been poured on the weevils, the weevils were dried with blotter paper, transferred to containers and held in a controlled temperature and humidity room for 24 hours. Counts were then made to determine the number of weevils killed (which includes moribund weevils). Several replicates were conducted, several concentrations of the test compound in the solution being used at each concentration. Table I sets out the L0 concentrations of the compound of the invention with respect to these weevils.

The compound of the invention also was tested to determine its toxicity with respect to mosquito (Anopheles albimanus) larvae, as follows: sufiicient of a 1% acetone solution of the test compound was dissolved in 100 milliliters of water to provide the desired concentration of the compound. Ten third-instar A. albz'manus larvae were introduced into each of two replicates. The larvae were exposed to the solution of the test compound for twentyfour hours, then mortality counts were made. Various concentrations of the test compound were used to determine the concentration required to kill approximately 50% of the 1arvae-i.e., the LC concentration, expressed in parts by weight of test compound per million parts by weight of the solution. The LC concentrations of compounds of the invention with respect to these mosquito larvae are set out in Table I.

TABLE I.MEDIAN LETHAL CONCENTRATION (L050) (GRAMS PER 100 MILLILIIERS OF SOLVENT) 1 Parts per million by weight of the solution.

EXAMPLE III The long life of the insecticide of this invention when employed on surfaces exposed to the atmosphere was demonstrated by the following test:

A solution of that test material, in acetone, was applied by pipette to a petri dish, and the acetone was allowed to evaporate. The concentration of the test material in the solution and the amount of solution was controlled to give ten milligrams of test material per square foot of the surface of the petri dish. The dishes were held at F. and 5 0% relative humidity. Adult Anopheles albimanus mosquitoes were exposed for one hour to the treated dishes at intervals. At each exposure, ten mosquitoes were used on each of two replicates. It was found that the test material gave control (i.e., killing all of the mosquitoes) throughout the test period, which was 28 days.

EXAMPLE IV The carbamate of this invention was tested to determine its residual toxicity with respect to mosquitoes when applied to a mud surface. In these tests, a red laterite clay was used. Experiments have shown that it is a clay which has typical properties in deactivating insecticides sprayed thereupon. The dry clay was mixed with sufificient water to make a stiff cement and then was molded into a block. The blocks were air dried under controlled temperature and humidity until their weight had become stabilized. The test material was formulated as a wettable powder, the powder dispersed in water and the dispersion sprayed on the blocks to uniformly coat the surface with the desired dosage of the test material per square foot of block surface, in this caes the dosage being 200 milligrams of test material per square foot of the mud surface. Ten A. Albimanus adults of mixed sexes were confined to the test surface for 60 minutes, then transferred to holding con tainers provided with food. Mortality counts were made 24 hours lated. In the same manner, adult mosquitoes were exposed to the treated blocks at later times. It was found that 90% control of the mosquitoes was obtained for one week, with 20% control remaining at the end of the 4 weeks.

EXAMPLE V To demonstrate the effectiveness of the carbamate of the invention when applied to wood surfaces, it was tested as follows: a solution of the compound in acetone was sprayed upon the surface of plywood panels and test insects caged against the treated panels, one series of exposures being made immediately after application of the test material, and later series of exposures being made at weekly intervals thereafter. The test insects were adult houseflies and adult A. albimanus mosquitoes.

As a dosage of 50 milligrams of the test material per square foot of the surface of the wood, 100% control of houseflies was obtained throughout the 28-day test period.

EXAMPLE VI The effectiveness and long life of the insecticide of this invention in soil was demonstrated by the following tests.

An acetone solution of the test compound was sprayed onto soil, as the soil Was being tumbled in a mixer, so as to uniformly disseminate the test compound into the soil'and provide a concentration of 3.3 parts by weight of the test material per million parts by weight of the soil. The soil then was dried to remove the acetone, moistened with water and divided into jars. The jars were sealed and held at 72 F. One day after the soil had been placed in the jars, certain of the jars were opened and third instar larvae of the western spotted cucumber beetle (Diabrotica undecimpunctata) were introduced into the soil. The jars were sealed, held for 24 hours, then the mortality of the larvae was determined. This procedure was repeated at weekly intervals after introduction of the treated soilv into the jars.

It was found that the test compound gave 100% control of the larvae for 21 days and 80% control at the end of 63 days.

The compound of this invention can be employed for insecticidal purposes by the use of any of the techniques which are conventionally employed in the art, with due regard to the particular application contemplatedi.e., whether the compound is to be applied to the surfaces of plants, buildings and the like, and including the surface of soil, and absorptive materials such as paper, sand, bricks, concrete, plaster, plant materials used in buildings, and the like, whether it is to be disseminated into soil, whether it is to be incorporated into surface coatings, such as waxes, resins, paints, lacquers, varnishes, whether it is to be incorporated in various plastic materials, including plastic sheetings, in order to obtain packaging and wrapping materials themselves resistant to insect attack and able to protect objects packed in them from such attack, or whether it be used in some other manner such as to exploit the long life of compounds of the invention.

When the compound of this invention is to be used as a conventional insecticide applied to surfacesof plants, buildings, soil and other absorptive materials or the like the compound can either be sprayed or otherwise applied in the form of a solution of dispersion, or it can be absorbed on an inert, finely divided solid and applied as a dust. Useful solutions for application by spraying, brushing, dipping, and the like can be prepared by using as the solvent any of the well-known inert horticultural carriers, including neutral hydrocarbons such as kerosene and other light mineral oil distillates of intermediate viscosity and volatility. Adjuvants, such as spreading or wetting agents, can also be included in the solutions, representative materials of this character being fatty acid soaps, rosin salts, saponins, gelatin, casein, long-chain fatty alcohols, alkyl aryl sulfonates, long-chain alkyl sulfonates, phenolethylene oxide condensates, C to C amines and ammonium salts, and the like. These solutions can be employed as such, or more preferably they can be dispersed or emulsified in water and the resulting aqueous dispersion or emulsion applied as a spray. Solid carrier materials which can be employed include talc, bentonite, lime, gypsum, pyrophyllite and similar inert solid diluents. If desired, the compound of the present invention can be employed as an aerosol, as by dispersing the same into the atmosphere by means of a compressed gas.

The concentration of the compound to be used with the above carriers is dependent upon many factors, including the carrier employed, the method and conditions of application, and the insect species to be controlled, a proper consideration and resolution of these factors being within the skill of those versed in the insecticide art. In general, however, the compound of this invention is effective in concentrations of from about 0.01 to 0.5% based upon the total weight of the composition, though under some circumstances as little as about 0.00001% or as much as 2% or even more of the compound can be employed with good results from an insecticidal standpoint, for example, up to 25% of the compound as wherein high concentrations of active material are used in low-volume sprays or dusts.

The compound of this invention is employed as a soil insecticide by conventional techniques which insure uniform intimate dissemination of an effective dosage of the compound in the soil. Judging by the experimental work which has been performed, the insecticidally effective dosages of the compound of the invention lie in the range of a few parts per million parts by weight of the soil. Thus, the effective dosages appear to lie Within the range of from about one or two parts, up to about fifty to one hundred parts per million, on a weight basis based on the weight of the air-dry soil. This is not to say that in some cases, a higher dosageof up to as much as 500 parts by million on the same basis-may not be used to advantage, but in most cases the effective dosage appears to lie within the range of from about 2 to about 50 parts per million on that basis. In more practical terms, the effective dosage appears to amount to from about 0.25 to about pounds of the insecticide per acre of land, depending upon the depth of soil to be treated, which may be as great as 6, or 8, or even 12 inches, depending upon the particular species of plants and insecticides involved. Generally, dosages of from about 1 to about 10 pounds of the insecticide per acre of land are preferred.

The compound of the invention is a solid at ordinary atmospheric temperatures. It may be applied to the soil neatas by grinding the solid insecticide, then admixing the resulting dust or powder with the soil to be treated. (The powdered insecticide is advantageously pre-mixed with an inert particulate diluent to aid in uniform dissemination of the insecticide in the soil.) Alternatively, the insecticide may be dissolved and/ or dispersed in a suitable liquid diluent and the solution or dispersion applied to and mixed With the soil, or the insecticide may be formulated with a suitable solid carrier and applied as a dust, powder or as granules to the soil and admixed therewith. The carbamate is not very soluble in water, so that water is not a suitable solvent. By the use of suitable emulsifying and dispersing agents, however, the carbamate can be emulsified or dispersed in water and the emulsion applied to the soil to be treated to provide effective control of the insect therein. Any of the usual emulsifying and dispersing agents commonly employed in forming aqueous emulsions and suspensions of water-insoluble materials can be used for this purpose. Generally but a small concentration of the emulsifying agent is required, as little as 0.05 percent of the weight of the final formulation being effective in many cases, while seldom will more than about 10% of the weight of the final formulation be required. Usually, the concentration of the emulsifying or dispersing agent will be from about 0.5 to about 5 percent of the weight of the formulation. Alternatively, or in addition, in some cases it may be to advantage to dissolve the carbamate or carbamatcs to be used in a solvent which can readily be dispersed in water to produce a heterogenous dispersion of the insecticide in the water.

Where the carbamate insecticide is to be applied as a solution, suitable solvents include water-immiscible alcohols, ketones and aromatic hydrocarbons, such as, for example, isopropyl alcohol, benzene, acetone, methyl ethyl ketone, secondary butyl alcohol, kerosene, chlorinated hydrocarbons, various non-phytotoxic hydrocarbon fractions which are ordinarily used in disseminating agricultural chemicals, including spray oils, horticultural oils, and the like.

The suitable solid carriers ordinarily are those which are essentially inert in the soil and which are not hygroscpic--for if they are hygroscopic the final formulation will not remain dry and free-flowing. In some cases, however, it may be desirable to employ as carrier a solid which is not inert-as, for example, a solid fertilizer such as a commercial mixed solid fertilizer, rock phosphate, urea or the like. Suitable inert carriers are those well known to the art including the clays such as the kaolinites, the bentonites and the attapulgites; other minerals in natural state such as talc, pyrophyllite quartz, diatomaceous earth, fullers earth, chalk, rock phosphate and sulfur; and chemically modified minerals, such as acid washed bentonites, precipitated calcium phosphates, precipitated calcium carbonate and colloidal silica. These diluents may represent a substantial portion, for example, 50 to 98 percent by weight of the entire formulation.

These solid formulations can be prepared by grinding or air-milling the carrier and insecticide together. Alternatively, the solid formulations can be formed by dissolving the insecticide in a suitable solvent, such as a volatile solvent, impregnating and/or coating the particles with the solution and if necessary, removing the solvent. The formulation also can be effected by melting the insecticide and mixing the molten insecticide with the carrier. Granular formulations can be prepared by impregnating and/ or coating granules of the carrier with the insecticide or by forming granules of mixtures of the insecticide and carrier.

From the standpoint of mechanics, the insecticide, neat or as a formulation, is applied to the soil in any manner which enables its intimate admixture with the soil to be treated. Thus the insecticide, which includes formulations thereof, can be applied to the surface of the soil,

or it can be applied below the surface of the soil, and then admixed with the soil. If in the form of a liquid formulation, the insecticide can be drenched onto the surface of the soil or injected into the soil. In other words, conventional means, well known in the art, can be used to effect intimate admixture of the insecticide with the soil to be treated.

The carbamate of this invention is characterized by an extended effective life in the soil and essentially no phytotoxicity at the insecticidally effective dosages. Consequently, it may not in all cases be necessary to treat the entire mass of insecticide-infested soilin some cases it may be sufficient to treat only the soil of the rhizosphere of the plants to be protected. Thus, the soil immediately surrounding the roots of established trees can be treated to protect the trees, and row crops can be protected by treating only the soil which will surround the roots of the plants in each before the seeds or plants are planted, or after the plants have been planted. The formulations of the insecticide can also contain other materials, such as nematocides, fungicides, insecticides of different action and/or different physical characteristics, hormones, and/ or fertilizers, to form multipurpose compositions.

The carbamate of this invention also can be used to control soil-dwelling insects by treating seed with the carbamate.

We claim as our invention: 1. 3,4-dimethyl-S-ethylphenyl-methylcarbamate.

References Cited UNITED STATES PATENTS 3,062,707 11/1962 Kohn et a1 260479C 3,130,122 4/1964 Kuderna et al 260-479C 3,131,215 4/1964 Lemin et al. 260479C FOREIGN PATENTS 223,028 7/1959 Australia 260-479 OTHER REFERENCES Kalbezen et al.: Journal of Agricultural and Food Chemistry, vol. 2, pages 864-870 (1954).

JAMES A. PATTEN, Primary Examiner US. Cl. X.R. 424300 

